Police investigating leaks of A-level maths exam papers have referred a file of evidence to the Crown Prosecution Service (CPS), which will consider bringing criminal charges.

The file dates back to a leak in 2017, when the exam board Edexcel was forced to issue replacement questions at the last minute to a limited number of exam centres after reports that some students had access to content in advance.

The following year another maths A-level paper was reported to have been leaked online a day before thousands of candidates were due to sit the exam. Pearson, which owns Edexcel, said an investigation into the 2018 leak was continuing but it hoped police would send a second file to the CPS shortly.

Making the announcement in the run-up to this summer’s exams, Pearson said it hoped its update would act as a deterrent to anyone considering similar action, and would show that perpetrators would be held to account for the disruption caused.

In a letter to headteachers in advance of this summer’s exams, Pearson also outlined measures it has taken to enhance security this summer, which includes tracking technology for question papers, extra inspections of exam centres and additional labelling to question paper packages to avoid errors.

Pearson is also piloting an additional digital solution, which it describes as “micro technology”, to monitor the integrity of question paper packets. “This uses technology that will allow us to track the date, time and location of packages in the extremely unusual event that they should be opened early.”

Pearson described the 2017 and 2018 leaks as “a limited external breach” but in 2017 Sharon Hague, a vice-president of Pearson, wrote to headteachers expressing regret, admitting the situation had resulted in “anxiety for schools, teachers, students and their parents”.

Pearson revealed the progress made on the two cases in a statement on Tuesday, but said the investigations had been time consuming due to their complexity and unusual nature.

The statement said: “In the UK summer examination series in 2017 and 2018, Pearson was subject to a limited external breach of its maths A-level paper. The police have made progress in their investigation from the first limited breach and have referred the first case to the CPS.

“They are also finalising their investigation with the second case and we hope that they will soon be sending materials to the CPS. We hope this latest update will act as a deterrent for any other isolated individuals that consider this course of action.”

It went on: “We have continued to support the police in their investigations, but due to the complexity and unusual nature of these cases, it has taken time to investigate. The police informed us that in February, they referred the first case to the CPS with the aim of bringing charges against those arrested.

“The individuals responsible for these incidents are therefore now being held to account for the disruption that they caused. The police are finalising the second case and we hope that they will soon be sending materials to the CPS.”

According to reports at the time, the 2018 leak saw one of the Edexcel maths A-level papers leaked online a day before thousands of candidates were due to sit the exam. Students reported seeing the paper for sale online for £200, with the sellers sending over the first question to prove they had it, but demanding the cash before they would reveal the rest.